commit: warn the user when a commit already exists
Sometimes, a commit will result in an exact match of a preexisting
commit, and if that commit isn't a branch head, hg will incorrectly
note that it created a new head. Instead, we should warn the user that
commit already existed in the repository.
In practice, this bug is rather uncommon, and will only occur when the
usr explicitly sets the date.
Please note that this commit contains an API change to
cmdutil.commitstatus()
Differential Revision: https://phab.mercurial-scm.org/D9257
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true